Conventionally, there exists a battery apparatus obtained by connecting in parallel a plurality of storage batteries, each of which includes a plurality of electric storage elements connected in serial to have the high voltage, so as to realize increase in capacity. In a case where the plurality of storage batteries is connected in parallel, when electric-storage states of the storage batteries are different from each other, there exists in this electric storage apparatus a risk that overcurrent flows from a storage battery having a high electric potential to a storage battery having a low electric potential, thereby leading to breakage.
Thus, there exists an electric storage apparatus in which storage batteries having small potential difference are connected in parallel when a plurality of storage batteries is to be connected in parallel and their electric potentials are equalized so as to suppress breakage caused by the above overcurrent (see Japanese Unexamined Patent Application Publication No. 2014-514692, for example).
However, the conventional electric storage apparatus connects in parallel storage batteries having small potential difference with each other without considering a startup aim of the electric storage apparatus, and thus there exists, in some cases, a case where storage batteries according to the startup aim are not connected in parallel to perform charge and discharge.